Never tried this test before. Tonight I connected the Apple DAC/AMP dongle to my IPAD and my DFR to my MacBook. I compared several Classical large orchestral tracks:
Mahler, Beethoven and Brahms
Listening with my Sure 1540s I was surprised that the differences were subtle but noticeable. Mostly it was slightly more clarity and openness in the upper midrange. With the Sure at 47 Ohms power was no issue with either. At a price differential of about $190 the Apple dongle was quite good. However I’ll still choose the DFR for its marginal mid range openness and clarity. I’m guessing that a comparison with 300-600 Ohm headphone might tip it to the DFR even more conclusively with the larger power source on the MacBook or desktop.